Basic sulfurized calcium alkylphenates are used as compounding agents or additives in lubricating oils to neutralize harmful acids in internal combustion engines and to inhibit corrosion, gum formation and piston ring sticking caused by oxidation of the lubricating oil and oxidative polymerization of the engine fuel residues. Metal sulfonates are commonly used in lubricating oil compositions as additives, rust inhibitors and detergents. It is highly desirable for such phenates or sulfonates to provide neutralization capacity for acids formed in engine combustion without too rapid loss in alkalinity. In some cases, these compounding agents or additives are overbased, containing a molar excess of base over that needed to neutralize the phenolic material or sulfonic acid.
A problem associated with the preparation of over-based additive compounds is that of the incompatibility of the mixture of the alkaline earth metal phenate and the sulfonate as a final product. The overbased materials, generally an alkaline earth metal compound, generally a carbonate, are dispersed in the alkaline earth metal dispersing agent, the amount of dispersed alkaline earth metal being known as the overbased amount. Since the greater the basicity of the material the better, as this allows smaller amounts of the material to be used for a given effect in a lubricant, a greater degree of overbasing is highly desirable. However, to increase basicity, it is generally necessary to increase the dispersed alkaline earth metal content of the carbonate complex.
A highly desirable object of overbasing additive agents is to obtain the overbased additive agents in the form of extremely fine particles in a finely dispersed colloidal form such that the lubricant compositions containing the overbased additive agents are stable, are haze-free, are gellation-free and are not subject to appreciable thickening in the absence of promoters.
The instant invented process relates to increased carbonation of an alkaline earth metal phenate and ammonium sulfate to give a resulting product with improved solubility, due to overcoming incompatibility of the phenate and sulfonate.
Overbased phenates, including sulfurized phenates, are commonly manufactured in the presence of ethylene glycol which must be removed from the product. The presence of glycol in overbased phenates can cause engine varnish or lacquer. Phenates are generally the reaction product of phenol or substituted phenol with a metal or ammonium base. Often the metal base is a Group II metal compound. Substituted phenols are generally mono-, di- or tri-hydrocarbyl substituted, such as alkyl, alkenyl, aryl, aralkyl, or alkaryl. Monoalkyl substitution is preferred. The hydrocarbyl can comprise low molecular weight groups such as methyl, ethyl, the isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and the like up to high molecular weight materials having a number average molecular weight of 10,000 or more. These hydrocarbyl substituents can be intermediate molecular weight polymer olefins such as C.sub.8 -C.sub.100 ethylene or propylene or butene polymers. The hydrocarbyl can be substituted with groups such as chlorine, bromine, hydroxy, nitro or sulfonic acid groups so long as such substitution does not interfere with the utility of the composition. The Group II metal compound can comprise a metal oxide, hydroxide, alcoholate, acetate and the like. Common metals are calcium, barium, strontium and magnesium. Often, the metal compound is calcium oxide or hydroxide. Phenates can contain sulfur which can be introduced by reaction of elemental sulfur or SCl.sub.2 with phenol or substituted phenol, or by the reaction of elemental sulfur or SCl.sub.2 with metal phenate.
Methods of making these various phenates and sulfur-containing phenates and overbasing can be found in U.S. Pat. Nos. 2,680,096; 3,036,971; 3,178,368; 3,336,224; 3,437,595; 3,464,970; 3,761,414; 3,801,507; 3,810,837; 3,923,670; 3,932,289; 3,953,519; 3,966,621 and 3,969,235.
Oil soluble overbased sulfonates are made by reacting a base with oil-soluble sulfonic acids. Suitable oil-soluble sulfonic acids can be aliphatic or aromatic compounds. Suitable aromatic sulfonic acids are the oil-soluble petroleum sulfonic acids, commonly referred to as "mahogany acids," aryl sulfonic acids, and alkylaryl sulfonic acids. Illustrative of such sulfonic acids are dilauryl benzene sulfonic acid, lauryl cetyl benzene sulfonic acid, paraffin-substituted benzene sulfonic acids, polyolefin alkylated benzene sulfonic acids, such as polybutylene alkylated benzene sulfonic acids in which the polybutylene substituents have a molecular weight of at least about 100, and preferably within the range of from about 100 to about 10,000, and polypropylene alkylated benzene sulfonic acids in which the polypropylene substituents have a molecular weight of at least about 80 and preferably within the range of from about 80 to about 10,000. Examples of other suitable sulfonic acids are alpha-olefin benzene sulfonic acids, diparaffin wax-substituted phenol sulfonic acids, acetyl chlorobenzene sulfonic acids, cetyl-phenol disulfide sulfonic acids, cetyl-phenol monosulfide sulfonic acids, and cetoxy capryl benzene sulfonic acids. Other suitable oil-soluble sulfonic acids are well described in the art, such as, for example U.S. Pat. No. 2,616,604; U.S. Pat. No. 2,626,207; and U.S. Pat. No. 2,767,209; and others.
Non-aromatic sulfonic acids are generally made by the sulfonation of most any aliphatic hydrocarbon such as alkanes, alkenes, and the like. Also, the hydrocarbyl may contain various substitutions which do not interfere with later reactions or end use. One preferred group of non-aromatic sulfonic acids is made by the sulfonation of polymers or copolymers, such as polymerized or copolymerized olefins.
The term "polymer olefins" as used herein refers to amorphous polymers and copolymers derived from olefinically unsaturated monomers. Such olefin monomers include olefins of the general formula RCH.dbd.CH.sub.2, in which R comprises hydrogen or an aliphatic or cycloaliphatic radical of from 1 to about 20 carbon atoms, for example, propene, isobutylene, butene-1, 4-methyl-1-pentene, decene-1, vinylidene norbornene, 5-methylene-2-norbornene, etc. Other olefin monomers having a plurality of double bonds may be used, in particular diolefins containing from about 4 to about 25 carbon atoms, e.g., 1,4-butadiene, 2,3-hexadiene, 1,4-pentadiene, 2-methyl-2,5-hexadiene, 1,7-octadiene, etc. These polyolefins have number average molecular weights from about 36 to about 10,000 or higher, but preferably from about 80 to about 10,000. Of these materials, a preferred group is polyethylene or polypropylene or polybutylene polymers. The olefin may be a copolymer, such as an ethylene propylene copolymer or ethylene-propylene-hexadiene terpolymer, or others.
The preparation of the sulfonic acids is well known. Such sulfonic acids can be prepared by reacting the material to be sulfonated with a suitable sulfonating agent, such as concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid or sulfur trioxide for a period of time sufficient to effect sulfonation, and thereafter separating insoluble acid sludge from the oil-soluble sulfonic acid. Overbased sulfonates are commonly made by the reaction of sulfonic acid with metal bases such as the oxide, hydroxide, or carbonate of calcium, magnesium or barium. In some cases, the sulfonate can be made from the metal itself or a derivative of said metal. Suitable processes for making overbased sulfonates are described in U.S. Pat. Nos. 3,126,340; 3,492,230; 3,524,814; and 3,609,076.
U.S. Pat. No. 4,412,927 teaches the preparation of detergent-dispersant compositions useful as additives for lubricating oils having a base of alkylbenzene sulfonates and sulfurized alkylphenates. The process employs sulfurized alkylphenates, alkaline-earth metal alkylbenzene sulfonates, alkylene glycols and carbon dioxide. The process requires carbonating at a temperature between about 100.degree. C. and 250.degree. C., a reaction medium comprising a sulfurized alkylphenate of an alkaline earth metal of a total basic number (TBN) (ASTM Standard D-2896) of between 0 and 170, the said alkylphenate having one or more C.sub.6 -C.sub.60 alkyl substituents, an alkaline earth metal alkylbenzene sulfonate of a molecular weight of more than about 300 and a TBN of less than or equal to about 150, an alkaline earth metal compound, an alkylene glycol and a diluent oil. The alkylene glycol is subsequenty removed and the metallic detergent-dispersant is separated.
As is well-known, calcium phenates having TBN's of 80-250 tend to interact with low and high base sulfonates to produce haze and sediment when blended into crankcase oils. This phenate-sulfonate incompatibility can be influenced by the components in a finished oil. For example, the simultaneous presence of zinc dialkyldithiophosphate (ZnDTP) and water can aggravate the phenate-sulfonate interaction. Many finished oils contain ZnDTP. This phenate-sulfonate incompatibility is worsened when the finished oil contains a small amount of water, as can happen during handling and storage.
It has long been known, as evidenced by the preceding recital of the prior art, i.e., U.S. Pat. No. 4,412,927, that an overbased metallic detergent-dispersant can be prepared by carbonating a sulfurized alkylphenate of an alkaline earth metal having a TBN of between 0 and 170, an alkaline-earth metal alkylbenzene sulfonate having a molecular weight of more than 300 and a TBN of less than or equal to 150, an alkaline-earth metal compound, an alkylene glycol and a diluent oil. The resulting product requires removal of the alkylene glycol which can waste raw materials. Incomplete removal of the alkylene glycol can cause engine varnish.
In our process, we have found unexpectedly that if an alkaline earth metal phenate is reacted with an alkylbenzene ammonium sulfonate in the presence of a monoalcohol selected from the group consisting of alcohols of one to four carbon atoms, the resulting product as an overbased composition has improved phenate-sulfonate compatibility. The monoalcohol can be in an alcohol-water solution. These so-called cosynthesized phenate-sulfonates in an overbased state have improved solubility in lubricating oils, particularly in the presence of small amounts of water, are stable colloidal dispersions, are haze-free, are gellation-free, non-viscous and are not subject to appreciable thickening in the absence of promoters. The introduction of carbon dioxide into the cosynthesized phenate-sulfonate mixture can be in any suitable manner such as in the form of an overbased phenate or, preferably, by carbonating under suitable conditions the cosynthesized phenate-sulfonate mixture in the presence of the monoalcohol of one to four carbon atoms.
We have found that optimization of carbonation provides improved water tolerance in lubricating oil additives.
Accordingly, in the prior art it has been taught that a mixture of a sulfurized alkylphenate and an alkaline-metal alkylbenzene sulfonate can be prepared in the presence of an alkylene glycol or a monoalcohol having a boiling point of 120.degree. C. or greater. However, there has been no recognition in the prior art that an improved overbased metallic detergent-dispersant can be prepared in a cosynthesis reaction from a calcium phenate and an alkylbenzene ammonium sulfonate in the presence of a C.sub.1 to C.sub.4 alcohol, preferably methanol or a methanol-water mixture wherein the calcium phenate and alkylbenzene ammonium sulfonate preferably are overbased together or the phenate is in an overbased state and degree of carbonation is optimized.